D-amphetamine and other psychopharmacological agents are increasingly being used in the treatment of childhood behavioral dis- orders. The present proposal aims to increase out understanding of the age-dependence of some of the biochemical effects of these drugs. Many neuropharmacological agents seem to produce their behavioral effects by modifying the metabolism of monoamine neurotransmitters in the central nervous system and in the peripheral nervous system. There is abundant evidence that such monoaminergic neurons are not fully mature at birth in non-precocial animals (i.e., humans and rats) - They are less able to synthesize, store, inactivate, release, and respond to neurotransmitters than are corresponding neurons in adult animals. Moreover, not all of their synaptic connections have been made. Relatively little information is currently available concerning possible relationships between the degree of functional maturity of these neuronal populations and their participation in the physiological and behavioral effects of the amphetamines. Support is requested to study the biochemical mechanisms responsible for the changes in behavior and physiology following amphetamine administration to developing animals. Proposed experiments will examine the possibilities of a) differential drug metabolism; b) altered drug disposition; c) differential effects on the uptake, synthesis, storage, inactivation and release of the putative neurotransmitters; or d) differential effects resulting from the immaturity of neuronal interconnections in the developing organism.